1. Field of the Invention
The present invention relates to a developer bearing member, a method for producing a developer bearing member, a developing device, an image-forming apparatus, and a computer system.
2. Description of the Related Art
As one type of an image-forming apparatus, there is known an apparatus comprising a rotary-type developing unit. This rotary-type developing unit comprises a plurality of developing devices arranged radially about its axis of rotation. The developing devices are capable of developing a latent image formed on a photoconductor using developer, such as toner. When an image signal is transmitted from an external device such as a host computer, the image-forming apparatus makes the developing unit rotate about its axis of rotation in order to locate one of the plurality of developing devices in a developing position opposing the photoconductor. A toner image is formed by developing the latent image formed on the photoconductor, and the image is transferred to an intermediate medium. A color image is formed by superimposing the plurality of toner images, by sequentially changing the plurality of developing devices and repeating the above-mentioned developing and transferring processes.
(1) In order to realize such functions as to develop a latent image formed on a photoconductor as mentioned above, a developing device comprises, for example: a developing roller, which serves as a developer bearing member for bearing toner; a toner reservoir; a toner supplying roller; and a restriction blade. In order to enhance performance for bearing and/or delivering toner, a multitude of depressions are formed on the surface of the developing roller. These depressions can be formed by, for example, blasting using spherical particles, such as glass beads, and the like.
If the surface roughness of the depressions formed by blasting or other methods is small (in other words, if the surface of each depression is not so rough), a situation may occur in which the “tumbling property” of the toner bore by the depressions deteriorates (in other words, the toner will not tumble sufficiently in the depressions). Such a situation occurs because the area of contact between the toner and the surface of the depression is large due to the fact that the surface roughness of the depressions is not sufficient.
The deterioration of the tumbling property may bring about various problems. For example, when the toner carried (bore) by the developing roller is charged by a developer charging member, such as the restriction blade, there is a problem that the toner charge is not sufficient due to the deterioration in the tumbling property. Another example may be that, when the toner remaining on the developing roller after development of the latent image is to be stripped off by a developer stripping member, such as the toner supplying roller, the toner cannot be stripped off sufficiently due to the deterioration in the tumbling property.
Therefore, a way of improving the tumbling property of the toner has been desired.
(2) Further, as explained later, a multitude of protrusions may be provided on the surface of the depressions as a method of avoiding deterioration of the tumbling property of toner. By providing these protrusions, the surface of the depressions will become coarse, and since the area of contact between the toner and the surface of the depression will become smaller, it becomes possible to improve the tumbling property of the toner.
Among the toner particles, there exist so-called “pulverized toners”. A “pulverized toner” is smaller than toners having a particle size sufficient for developing the latent image formed on an image bearing member. These pulverized toners tend to be produced particularly when manufacturing toner according to the grinding method. Pulverized toners will increasingly be produced if a lubricant is mixed to the toner, since the toner becomes susceptible to cracking.
When toner is bore by the developing roller, there is a possibility that the toner (and mainly the pulverized toner) gets trapped between the protrusions. In this case, there is a possibility that the toner will keep accumulating at the same position on the surface of the developing roller, and degradation of toner will proceed, causing problems such as the so-called “filming phenomenon”.
In order to avoid such a situation, a way of preventing the toner (mainly the pulverized toner) from getting trapped in the developing roller has been desired.
(3) Meanwhile, in order to realize functions such as to develop a latent image formed on a photoconductor as mentioned above, another type of developing device comprises, for example, a developing roller, which serves as a developer bearing member for bearing toner, and a toner supplying roller and a restriction blade, which serve as an abutting member that abuts against (or contacts) the developing roller. In order to enhance performance for bearing and/or delivering toner, a multitude of depressions are formed on the surface of the developing roller. These depressions can be formed according to, for example, a blasting treatment using spherical particles, such as glass beads, and the like.
If the surface roughness of the depressions formed by blasting or other methods is small (in other words, if the surface of each depression is not so rough), a situation may occur in which the “tumbling property” of the toner, which is bore by the developing roller, at the abutting section where the abutting member and the developing roller abut against each other deteriorates (in other words, the toner will not tumble sufficiently in the depressions). Such a situation occurs because the area of contact between the toner and the surface of the depression is large due to the fact that the surface roughness of the depressions is not sufficient.
The deterioration of the tumbling property may bring about various problems. For example, when the toner bore by the developing roller is charged by a developer charging member (which also serves as the above-mentioned abutting member) at the abutting section where the developer charging member and the developing roller abut against each other, there is a problem that the toner charge is not sufficient due to the deterioration in the tumbling property. Another example may be that, when the toner remaining on the developing roller after development of the latent image is to be stripped off by a developer stripping member (which also serves as the above-mentioned abutting member) at the abutting section where the developer stripping member and the developing roller abut against each other, the toner cannot be stripped off sufficiently due to the deterioration in the tumbling property.
Therefore, a way of improving the tumbling property of the toner has been desired.